1. Field of the Invention
The invention relates to a gas filling system that fills a gas tank mounted on, for example, a vehicle with gas from a gas filling device installed in, for example, a hydrogen station.
2. Description of the Related Art
A vehicle equipped with a gas tank makes a stop at a gas station for gas filling, and gas is filled into the gas tank from a filling nozzle of a gas filling device. In the case of hydrogen gas, the temperature and pressure increase in the gas tank as the hydrogen gas is filled into the gas tank, so it is necessary to regulate the filling amount so that these temperature and pressure do not exceed respective reference values. In terms of this point, Japanese Patent Application Publication No. 2007-147005 (JP-A-2007-147005) describes a technique that the temperature in a hydrogen tank is measured during hydrogen filling and then a filling path is changed to a filling path with a precooler when the temperature is higher than a predetermined value to thereby suppress an increase in temperature and ensure a sufficient filling amount.
Incidentally, the degree of increase in temperature in a gas tank during filling significantly varies depending on the heat radiation property of the gas tank. A gas tank that has an excellent heat radiation property allows a filling rate (filling flow rate) to be increased, and, by so doing, a period of time for filling may be reduced. However, the technique described in JP-A-2007-147005, the heat radiation property of a gas tank and a period of time for filling are not considered, so there is still room for improvement. In addition, Japanese Patent Application Publication No. 2005-127430 (JP-A-2005-127430) describes a method in which a maximum filling rate corresponding to the shape and capacity of a gas tank is prestored in a database at a gas station and then the maximum filling rate is loaded during filling. According to this method, it is necessary to update the database each time a new gas tank is developed, so it is realistically difficult.